Here the tapwater is GH=1, KH=8. The KH is almost completely from sodium bicarbonate, added by the water company to keep the deep artesian spring water from being too soft.
I used to experiment with burning off some KH with hydrochloric acid, producing both CO2 and sodium chloride. Salt levels during these experiments, some of which lasted for months, were generally equivalent to 1 to 2 tbsp. per 10G.
At one time or another during the hobby, I've had major fights with virtually every algae. Except BBA. Sure I've had it, but only minor amounts; easily removed and prevented from recurring.
Nothing conclusive, just a data point.